June 2016 Paper 1 Q8
8 Solve \(\qquad (3 - \sqrt{x})^{\frac{1}{3}} = -2\) [3 marks]
| Answer | Mark | Comments |
|---|---|---|
| \((-2)^3\) or \(-8\) seen | B1 | |
| \(-\sqrt{x} =\) (their \(-8\)) \(- 3\) or \(-\sqrt{x} = -11\) or \(\sqrt{x} = 11\) | M1 | |
| 121 | A1 |
Additional guidance
\(-2^3\) (no brackets) is B0 unless \(-8\) seen
For M1 it must say \(\sqrt{x} = \ldots\ldots\) or \(-\sqrt{x} = \ldots\ldots\) Note: ... (their \(-8\)) cannot be \(-2\)
... and it must be correct manipulation from their \(-8\)
eg \(\quad 3 - \sqrt{x} = (-2)^3\) or \(3 - \sqrt{x} = -8 \qquad\) B1
\(\sqrt{x} = -11 \qquad\) M0 (error in manipulating terms)
\(x = 121 \qquad\) A0 (correct answer from wrong working)